Storage cathode ray tube electron beam position indicator

ABSTRACT

Apparatus to display a cursor mark image which indicates the electron beam position of a storage cathode ray tube without storing the cursor mark image along with information desired to be stored. To generate the non-storing cursor mark image this apparatus uses a second cathode ray tube, the electron beam of which is deflected substantially in parallel with the electron beam of the storage cathode ray tube. The cursor mark image produced by the second cathode ray tube and the information image produced by the storage cathode ray tube are then optically aligned and simultaneously displayed on a viewing screen.

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[ 1 Feb. 6, 1973 [5 STORAGE CATHODE RAY TUBE Primary Examiner-Carl D. Quarforth ELECTRUN BEAM POSITION Assistant Examiner-J. M. Potenza HNDICATQR Attorney clarence R. Patty, Jr. and Walter S.

. Zebrowski [75] Inventor: Douglas A. Cotter, Raleigh, NC. [73] Assignee: Corning Glass Works, Corning, ABSTRACT Apparatus to display a cursor mark image which indicates the electron beam osition of a stora e 1 71 P g [22] Filed Jan 9 cathode ray tube without storing the cursor mark [21] Appl. No.: 104,244 image along with information desired to be stored. To

' generate the non-storing cursor mark image this ap- 1s 10, 178 6.8, 178 7.87" Pratus uses a Second cathode ray mbfie the 616cm)" e e e E g: 3 l 3/1/26 beam of which is deflected substantially in parallel 1581 F111 oi''riillllIIIIiIIIIIIii/l 7'19 7.87 7.7- M we beam of the eeeheee eey 315/10 tube. The cursor mark image produced by the second cathode ray tube and the information image produced [56] References Cited by the storage cathode ray tube are then optically aligned and simultaneously displayed on a viewing UNITED STATES PATENTS screen.

3,548,099 12 1970 Waybright.... ..l78/6.8 19 Claims, 5 Drawing Figures 2,481,622 9/1949 Rosenthal ..l78/7.87

X INFORMATION 1 SIGNAL 55 Y s ggsnnon 28 SIGNAL gENERATOR PATENTEDFEB 6|975 3,715,619

SHEET 2 OF 3 F F /'g. 5

INVLNI R. Doug/as A. Caller ATTORNEY STORAGE CA'IIIODE RAY TUBE ELECTRON BEAM POSITION INDICATOR BACKGROUND OF THE INVENTION This invention relates to apparatus for displaying, without storing, a cursor mark which indicates the position of the electron beam of a storage CRT (cathode ray tube).

In conventional CRTs an image written on the screen of the tube by electron beam excitation disappears rapidly after the electron beam excitation is removed. In some storage CRTs, however, the written image may persist for a long period of time after the electron beam excitation is removed and, therefore, it is possible for th e beam to write many different observable information images or messages at different locations on the screen of the tube at different times. In such a tube, all of the different images or messages even though written at different times may be visible on the screen of the tube at the same time. Furthermore, in the use of such storage tubes it is often desirable to have an image written at a specific location on the storage tube screen, and therefore, it may be necessary to move the electron beam before the image is written. Consequently, to avoid leaving undesirable connecting paths or images between each of the messages or information images, it is necessary that the electron beam intensity be decreased to a low enough level so that an image is not produced while said beam is moving between messages, and normally the electron beam intensity is held at said low level except when a message is actually being written on the storage tube. However, if the electron beam does not leave a visible image except when writing information it is impossible to know by observing the storage tube screen the location of the electron beam as the beam travels between messages. Therefore, it has become necessary to find some means of ascertaining the location of the electron beam even when the beam image is not visible.

SUMMARY OF THE INVENTION Briefly, the information display apparatus of this invention comprises an information storage CRT, and an external light source for projecting probing light to the screen of said storage CRT which probing light is modulated by the information image stored by said storage CRT and is then reflected therefrom. Also provided is a viewing screen upon which information is displayed, and a beam splitter which is oriented and aligned with the storage CRT, probing light source and viewing screen such that the information image produced by the storage CRT and transmitted by the modulated probing light may be displayed on the viewing screen. An auxiliary CRT is also provided, said auxiliary CRT being disposed and aligned such that the image produced by said auxiliary CRT may be displayed on said viewing screen simultaneously with the information image produced by the storage CRT. Further provided is means to deflect the electron beam of the storage CRT and the electron beam of the auxiliary CRT substantially in parallel such that the auxiliary CRT electron beam location corresponds to the storage CRT electron beam location.

An object of this invention is to display an image representing the position of the electron beam of a storage CRT without also storing said image along with the information desired to be stored.

Additional objects, features and advantages of the present invention will become apparent to those skilled in the art, from the following detailed description and attached drawings, on which, by way of example, only preferred embodiments of the invention are illustrated,

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic illustration of apparatus for displaying a non-storing cursor mark incorporating the teachings of this invention.

FIG. 2 is an enlarged fragmentary oblique view of a photochromic storage CRT.

FIG. 3 is an elevation view of a viewing screen taken along line 33 of FIG. 1.

FIG. 4 is a diagrammatic illustration of an alternate embodiment for displaying a non-storing cursor mark in accordance with this invention.

FIG. 5 is an elevation view of an auxiliary CRT taken along line 4-4 of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION For the purposes of the following detailed description, the invention will be described in connection with a storage CRT having a photochromic material as the storage medium, however, such a storage CRT is merely an example and other types of storage CRTs known in the art are suitable and may be used.

Referring to FIG. 1, a probing light source 10 projects light rays 12 through a beam splitter 14 onto the faceplate or screen 16 of a storage CRT (cathode ray tube) 18, shown in detail in FIG. 2, which uses a plate 20 of photochromic material as the storage medium. Storage by this type of CRT is accomplished by writing" information on the photochromic plate by darkening selected areas of the photochromic plate. The term photochromic material when used herein means material that darkens and becomes less transparent when subjected to light or other electromagnetic radiation having a wavelength within a first prescribed range, and bleaches or becomes more transparent when subjected to a wavelength of light or other electromagnetic radiation within a second prescribed range. A particularly effective photochromic material for use as the storage material in the practice of this invention is silver halide photochromic glass described in U.S. Pat. No. 3,208,860 by W. H. Armistead and S. D. Stookey. Plate 20 may be made of a single solid piece of photochromic material or said plate may be comprised of a plurality of optical fibers made of photochromic material arranged in parallel relationship such that the opposite ends of said optical fibers form the two broad surfaces of said plate. For a further discussion of the construction of photochromic plates and their use as a storage medium see U.S. Pat. No. 3,428,396 by GK. Megla and BF. Ludovici.

The probing light is selected so that it has a wavelength substantially outside of said first and second prescribed ranges and therefore neither tends to substantially darken or bleach the photochromic material. After probing light rays 12 enter storage CRT 18 through faceplate 16 they are transmitted through substantially transparent, undarkened or bleached areas of photochromic plate 20 toward the surface of dichroic layer 22. The dichroic layer is selected so that light rays with wavelengths substantially that of the probing light are reflected, and light rays with wavelengths substantially that emitted by phosphor layer 24 are transmitted. Therefore, light rays 12 from probing light are reflected from the surface of dichroic layer 22 back through the substantially transparent areas of photochromic plate and through faceplate 16 out of storage CRT 18 as light rays 26. It is to be noted that embodiments utilizing a photochromic glass plate as both the storage medium and the faceplate are entirely feasible in the practice of this invention.

Reflected light rays 26 again intercept beam splitter 14 where they are partially reflected and partially transmitted. Light rays 26 reflected from beam splitter 14 are transmitted through lens 28, and are then reflected by dichroic mirror 30 against a viewing screen 32. Lens 28, as illustrated in FIG. 1, is used to focus and magnify the storage tube image, however, it is entirely feasible that a lens could be used to only focus the image or to focus and reduce the image. Dichroic mirror 30 is selected so that light with a wavelength substantially that of the probing light is reflected, and light with a wavelength substantially that of the image from an auxiliary CRT hereinafter described is transmitted. Viewing screen 32 is illustrated as a rear view screen, however, a front view screen is entirely feasibly for use with this invention.

The substantially non-transparent dark areas or information images 34 on the photochromic plate 20, shown in FIG. 2 as an image of HOI-I, represents stored information written on the photochromic plate by light emitted from phosphor layer 24 which was excited by the electron beam 36 of storage CRT 18. Since neither projected light rays 12 nor reflected light rays 26 will be transmitted through these dark areas, said information images 34 transmitted by light rays 26 will be represented as shown in FIG. 3 on viewing screen 32 as dark areas 34 on a light background.

Information signal generator 38, shown in FIG. 1, provides the input electrical signals which deflect and position electron beam 40 of auxiliary CRT 42, and electron beam 36 of storage CRT 18 along X and Y coordinates. The signal applied to the X deflection coil of storage CRT 18 is the same signal applied to the X deflection coil of auxiliary CRT 42, and the signal applied to the Y deflection coil of storage CRT 18 is the same signal applied to the Y deflection coil of auxiliary CRT 42. Therefore, the electron beams of both CRTs are deflected substantially in parallel. The result of deflecting both electron beams in parallel is that at any instant in time the deflection of the auxiliary CRT electron beam corresponds to the deflection of the storage CRT electron beam. Parallel" deflection of the two electron beams may be achieved by connecting the X deflection coils in series, and connecting the Y deflection coils in series. Such connections are made in the embodiment shown in FIG. ll. Parallel deflection may also be achieved by connecting the X deflection coils in parallel and connecting the Y deflection coils in parallel. Such connections are made in the embodiment shown in FIG. 4 hereinafter discussed.

The image produced by the auxiliary CRT electron beam will hereinafter alternately be referred to as the cursor mark, and the auxiliary CRT producing said cursor mark will hereinafter alternately be referred to as the cursor CRT. As will be discussed further, the cursor mark is not necessarily simply an illuminated spot the CRTs at times when said electron beam is of That is, there is no flow of electrons or the flow of electrons is at such a low level there is no visible image produced by the CRT. Therefore, statements concerning electron beam deflection apply to electron beams in said of condition as well as high level electron beams which produce a visible image.

Referring again to FIG. 1, light rays 46 transmitting cursor mark image 44 are of a wavelength that is substantially totally transmitted by dichroic mirror 30. Light rays 46 transmitted through dichroic mirror 30 are substantially optically aligned with light rays 26, which are transmitting the information image from the storage CRT 18. The cursor mark image transmitted by light rays 46 and the image of stored information transmitted by light rays 26 are then simultaneously displayed on viewing screen 32 as images 44' and 34' respectively as shown in FIG. 3. Therefore, because the electron beams of both tubes are driven substantially in parallel and because light rays from both cathode ray tubes are optically aligned, the cursor mark image on the viewing screen which represents the location of the cursor CRT electron beam also corresponds to the location of the storage CRT electron beam.

The intensity of the cursor CRT electron beam image or cursor mark need not necessarily be at a visible level when the intensity of the storage CRT electron beam image is sufficient to write a visible image on the storage CRT. In fact, said intensity level of the cursor mark may preferably be decreased to a non-visible level or of when information is being written on the storage CRT and increased to a visible level or on only when the storage CRT is not writing information. To accomplish this type of intensity control it is necessary that the intensity control signal to the storage CRT and the intensity control signal to the cursor CRT be different signals. In fact, it may be preferable that the intensity control signals be out of phase. That is, as the storage CRT intensity control signal Z as shown in FIG. 1, increases the storage CRT electron beam image to a visible level or on condition, the cursor CRT intensity control signal Z will decrease the cursor CRT electron beam image to a non-visible level or off condition, and as Z decreases the storage CRT electron beam image to a non-visible level or of condition, Z will increase the cursor CRT electron beam image to a visible level or on" condition. The intensity level of the cursor mark may also, of course, be increased or decreased as desired by a manual control.

It is possible in some applications that even if the intensity of the cursor mark is increased to a high level, visibility of said cursor mark may be very low and not easily discernible. This is especially true if the viewing screen is displaying a large amount of stored information received from the storage CRT. Therefore, to make the cursor mark easily discernible under all situations flagging" means may be provided. Such flagging" may include a cursor mark in the shape of a small easily recognizable symbol, pulsating the intensity of said cursor mark or both. One means of providing cursor mark flagging" is to provide a cursor mark signal generator which operates and produces output signals only when storage CRT 18 electron beam is off, that is, when the image of said electron beam is not at a visible level. Therefore, in the embodiments illustrated by FIGS. l and 4 a signal may be applied through connecting means 50 from information signal generator 38 to cursor mark signal generator 48 to initiate operation of said cursor mark signal generator whenever the electron beam of said storage CRT is off. When operating, cursor mark signal generator 48 controls the intensity level signal applied to the cursor CRT electron beam and modulates the X and Y deflection signals from the information signal generator which are applied to the electron beam deflection coils of both CRTs. In the embodiment illustrated in FIG. 1, both cursor mark signal generator 48 and information signal generator 38 apply an X deflection signal to current summing amplifier 52, and a Y deflection signal to current summing amplifier 54. Said current summing amplifiers add a positive cursor mark signal generator deflection signal to the information signal generator deflection signal and subtract a negative cursor mark signal generator deflection signal from the information signal generator deflection signal and thereby supply a resulting output deflection signal to both electron beam deflection coils which is the algebraic sum of the two applied signals. Other suitable means which may be apparent to one skilled in the art may be used to provide an algebratic sum of two applied signals as hereinabove described and thereby modulate the information signal generator deflection signals with the cursor mark signal generator deflection signals. Such other means include but are not limited to simply connecting the deflection signals from the two signal generators in series, as is illustrated in FIG. 4. Other suitable modulating means may also be used. To aid and simplify the following discussion, any position of the cursor CRT electron beam which results solely from X and Y deflection signals received from information signal generator 38 will hereinafter be designated as the home" position. Since an image of the storage CRT electron beam is not visible except when said storage CRT is writing information, and since cursor mark signal generator 48 operates only when the electron beam of said storage CRT is of that is, not writing information, movement of the storage CRT electron beam by cursor mark signal generator 48 away from the home" position will not result in an image being written on the photochromic storage plate. The method of operation of cursor mark signal generator 48 which flags" the cursor mark image is not critical and many different acceptable types of signal generators may be apparent to one skilled in the art. However, a single operation cycle of two types of signal generators suitable for the purpose of flagging the cursor mark of the present invention is briefly described below. In both types the described operation cycle is rapidly repeated over and over whenever information is not being written on the storage tube, and if on and off intensity pulsating of the symbol is also desired operation of the generator is delayed for a period of time between selected cycles.

The first type of cursor mark signal generator controls the cursor CRT in the same manner an oscilloscope controls its CRT. That is, in a single operation cycle of the signal generator, both X and Y deflection signals are supplied at the same time, if desired, and in such a manner that the electron beam moves adjacent to or around the home" position in the necessary directions to draw" the desired symbol or character on the screen of the cursor CRT. After drawing the desired symbol, the electron beam returns to the home position ready to repeat the operation. Preferably the character drawn by the electron beam is only large enough to be easily recognized. Since in this type of signal generator the character is produced by only deflecting the electron beam in a pattern corresponding to said character, the intensity of the electron beam image must remain at a visible level throughout an operation cycle.

The second type of cursor mark signal generator controls the cursor CRT in substantially the same manner a television set controls its CRT. That is, in a single operation cycle, the electron beam is deflected in a small sweep pattern which starts at the home position and then returns to said home position after completing each sweep pattern. The outside dimen sions of this small sweep pattern need not be any larger than the outside dimension of the desired character or symbol and consequently will cover only a very small portion of the total CRT screen surface area at one time. In a typical sweep pattern a signal is applied to one of the deflection coils, either X or Y, which continually sweeps the electron beam back and forth a small predetermined distance. Between each complete sweep a signal is applied to the other deflection coil to move the electron beam a small incremental portion of a second predetermined distance in a direction orthogonal to the sweeping motion. The small incremental distances moved by the electron beam are cumulative. That is, each incremental movement moves the electron beam further and further away from the home" position. Therefore, the incremental movement continues until the total movement of the beam caused by said incremental movement is equal to the second predetermined distance. The electron beam then returns to the home" position ready to start a new sweep pattern. The intensity of the electron beam image must be coordinated with said sweep pattern so that said image intensity is at a visible level only during certain portions of each sweep. Therefore, as in a commercial television set, during a single sweep pattern the visible portions of each sweep cumulate to produce the desired character.

Referring now to FIG. 4, another embodiment of the present invention is illustrated. The probing light source 10, the storage CRT 18, the cursor CRT 42, the information signal generator 38, the cursor mark signal generator 48, and the viewing screen 32 are the same as described in connection with FIGS. 1, 2 and 3. However, in this embodiment the cursor CRT 42 is oriented so that light rays transmitting the electron beam image of said CRT are projected through beam splitter 102 where they are aligned with modulated light rays 104 reflected by said beam splitter 102. Light rays 104 transmit the information image produced by storage CRT 18. Beam splitter 102 used in this embodiment is dichroic. That is, light rays with a wavelength substantially that produced by the probing light source are partially reflected and partially transmitted, and light rays with a wavelength substantially that produced by the cursor CRT are substantially transmitted. The two aligned images of this embodiment are shown displayed directly on a rear view display screen 32. This embodiment also illustrates that the electron beams of both tubes may be deflected in ,parallel by connecting both X deflection coils in parallel and connecting both Y deflection coils in parallel, and that the X and Y deflection signals from information signal generator 38 may be modulated with X and Y deflection signals from cursor mark signal generator 48 by connecting said signal generators in series.

Even though the embodiments described above and illustrated by FIGS. 1 and 4 show specific components for projecting and aligning the two images on the viewing screen, any type of projection means that will display the aligned cursor mark image and information image is suitable for use with this invention, and such projection means might use any combination of front view screens, rear view screens, beam splitters, mirrors and lenses.

A specific example of apparatus which is in ac cordance with the teachings of the present invention follows. The following components are aligned and oriented in the same manner as that illustrated in FIG. 1 and function in the same manner as the components described in connection therewith: a probing light which emits a blue-green color of light of approximately 510 millimicrons; a beam splitter; a storage cathode ray tube which uses as the storage medium photochromic glass having a composition of the type described by Example 6 of co-pending application Ser. No. 801,562 by R. J. Araujo, said photochromic glass becomes dark when exposed to light with a wavelength of approximately 350 millimicrons and bleaches when exposed to light with a wavelength of approximately 590 millimicrons, said cathode ray tube further having a dichroic layer behind said photochromic layer that transmits 35 millimicron wavelength light such as that emitted by the phosphor layer of the CRT, and reflects the 510 millimicron wavelength light of the probing light; a lens to magnify and focus light reflected from said beam splitter; auxiliary CRT which produces a red colored image with a wavelength of approximately 550 millimicrons; a dichroic mirror which substantially reflects blue-green colored light with a wavelength of approximately 510 millimicrons and substantially transmits red colored light with a wavelength of about 650 millimicrons; an information signal generator; a cursor mark signal generator which uses a small sweep pattern method of operation for producing a cursor mark in the form of a cross; two current summing amplifiers; and a rear view display screen upon which the images of the conventional cathode ray tube and the storage cathode ray tube are displayed.

Although the present invention has been described with respect to specific details and certain embodiments thereof, it is not intended that such details be limitations upon the scope of the invention except insofar as set forth in the following claims.

lclaim:

1. An information display apparatus comprising an information storage cathode ray tube,

an external light source for projecting probing light to said storage cathode ray tube, said probing light being modulated by the information image stored a viewing screen,

a beam splitter aligned with said storage cathode ray tube, probing light source, and viewing screen such that at least a portion of said information image produced by said storage cathode ray tube and transmitted by said modulated probing light may be reflected from said beam splitter and displayed on said viewing screen,

an auxiliary cathode ray tube disposed and aligned such that an image produced thereby may be displayed on said viewing screen simultaneously with the information image produced by the storage cathode ray tube, and

means to deflect the electron beams of said storage cathode ray tube and said auxiliary cathode ray tube substantially in parallel.

2. The apparatus of claim 1 wherein said means comprises a signal generator for providing X and Y deflection signals, the X deflection signal output being connected to the X deflection coils of each of said cathode ray tubes, and the Y deflection signal output being connected to the Y deflection coils of each of said cathode ray tubes.

3. The apparatus of claim 2 wherein said X deflection coils are connected in series with each other and said Y deflection coils are connected in series with each other.

4. The apparatus of claim 2 wherein said X deflection coils are connected in parallel with each other and said Y deflection coils are connected in parallel with each other.

5. The apparatus of claim 2 wherein said means further comprises a second signal generator for providing X and Y deflection signals, the X deflection signal outputs of said generators being connected in series with each other and to the X deflection coils of each of said cathode ray tubes, the Y deflection signal outputs of each of said signal generators being connected in series with each other and to the Y deflection coils of each of said cathode ray tubes.

6. The apparatus of claim 5 wherein said X deflection coils are connected in series with each other and said Y deflection coils are connected in series with each other.

7. The apparatus of claim 5 wherein said X deflection coils are connected in parallel with each other and said Y deflection coils are connected in parallel with each other.

8. The apparatus of claim 5 wherein said second signal generator further provides an intensity signal which is applied to the electron beam of said auxiliary cathode ray tube such that the image produced thereby is pulsated.

9. The apparatus of claim 5 wherein said second signal generator controls the deflection signals applied to the electron beam of said auxiliary cathode ray tube such that the image produced thereby is in the form of an easily recognizable symbol.

10. The apparatus of claim 5 wherein said second signal generator controls the deflection and intensity signals applied to the electron beamof said auxiliary cathode ray tube such that the image produced by said auxiliary cathode ray tube is in the form of an easily recognizable pulsated symbol.

11. The apparatus of claim 1 wherein said means comprises first and second signal generators, and

first and second summing amplifiers, the X deflection signal outputs from each of said generators being connected through one of said summing amplifiers to each of the X deflection coils of said cathode ray tubes and the Y deflection signal outputs from each of said signal generators being connected through the other of said summing amplifiers to the Y deflection coils of each of said cathode ray tubes.

12. The apparatus of claim 11 wherein said X deflection coils are connected in series with each other and said Y deflection coils are connected in series with each other.

13. The apparatus of claim 11 wherein said X deflection coils are connected in parallel with each other and said Y deflection coils are connected in parallel with each other.

14. The apparatus of claim 1 further comprising a lens aligned to transmit said modulated probing light, and

a dichroic mirror which substantially reflects light of a wavelength of that produced by said probing light source and substantially transmits light with a wavelength of that of the electron beam image produced by said auxiliary cathode ray tube, said dichroic mirror and auxiliary cathode ray tube being disposed and aligned such that said auxiliary cathode ray tube electron beam image is projected through said dichroic mirror toward said viewing screen, said modulated probing light being substantially reflected toward said viewing screen on which said electron beam image and information image are simultaneously displayed.

15. The apparatus of claim 14 wherein the storage medium of said information storage cathode ray tube is a plate of photochromic glass comprising a plurality of optical fibers made of photochromic glass arranged in parallel relationship such that the opposite ends of said optical fibers form the two surfaces of said photochromic glass plate, and said means comprises first and second signal generators, and first and second summing amplifiers, the X deflection signal outputs from each of said generators being connected through one of said summing amplifiers to each of the X deflection coils of said cathode ray tubes and the Y deflection signal outputs from each of said signal generators being connected through the other of said summing amplifiers to the Y deflection coils of each of said cathode ray tubes.

16. The apparatus of claim 1 wherein said beam splitter is dichroic in that it partially reflects and partially transmits light with a wavelength of that produced by said probing light source and substantially wholly transmits light with a wavelength of that of the electron beam image produced by said auxiliary cathode ray tube, said auxiliary cathode ray tube being disposed such that said electron beam image is projected through said beam splitter and aligned with said information image.

17. The apparatus of claim 16 wherein the storage medium of said information storage cathode ray tube is a plate of photochromic glass comprising a plurality of optical fibers made of photochromic glass arranged in parallel relationship such that the opposite ends of said optical fibers form the two surfaces of said photochromic glass plate, and said means comprises first and second signal generators, and first and second summing amplifiers, the X deflection signal outputs from each of said generators being connected through one of said summing amplifiers to each of the X deflection coils of said cathode ray tubes and the Y deflection signal outputs from each of said signal generators being connected through the other of said summing amplifiers to the Y deflection coils of each of said cathode ray tubes.

18. The apparatus of claim 1 wherein the storage medium of said information storage cathode ray tube is a plate of photochromic glass.

19. The apparatus of claim 18 wherein the plate of photochromic glass comprises a plurality of optical fibers made of photochromic glass arranged in parallel relationship such that the opposite ends of said optical fibers form the two surfaces of said photochromic glass plate. 

1. An information display apparatus comprising an information storage cathode ray tube, an external light source for projecting probing light to said storage cathode ray tube, said probing light being modulated by the information image stored by said storage cathode ray tube and being reflected therefrom, a viewing screen, a beam splitter aligned with said storage cathode ray tube, probing light source, and viewing screen such that at least a portion of said information image produced by said storage cathode ray tube and transmitted by said modulated probing light may be reflected from said beam splitter and displayed on said viewing screen, an auxiliary cathode ray tube disposed and aligned such that an image produced thereby may be displayed on said viewing screen simultaneously with the information image produced by the storage cathode ray tube, and means to deflect the electron beams of said storage cathode ray tube and said auxiliary cathode ray tube substantially in parallel.
 1. An information display apparatus comprising an information storage cathode ray tube, an external light source for projecting probing light to said storage cathode ray tube, said probing light being modulated by the information image stored by said storage cathode ray tube and being reflected therefrom, a viewing screen, a beam splitter aligned with said storage cathode ray tube, probing light source, and viewing screen such that at least a portion of said information image produced by said storage cathode ray tube and transmitted by said modulated probing light may be reflected from said beam splitter and displayed on said viewing screen, an auxiliary cathode ray tube disposed and aligned such that an image produced thereby may be displayed on said viewing screen simultaneously with the information image produced by the storage cathode ray tube, and means to deflect the electron beams of said storage cathode ray tube and said auxiliary cathode ray tube substantially in parallel.
 2. The apparatus of claim 1 wherein said means comprises a signal generator for providing X and Y deflection signals, the X deflection signal output being connected to the X deflection coils of each of said cathode ray tubes, and the Y deflection signal output being connected to the Y deflection coils of each of said cathode ray tubes.
 3. The apparatus of claim 2 wherein said X deflection coils are connected in series with each other and said Y deflection coils are connected in series with each other.
 4. The apparatus of claim 2 wherein said X deflection coils are connected in parallel with each other and said Y deflection coils are connected in parallel with each other.
 5. The apparatus of claim 2 wherein said means further comprises a second signal generator for providing X and Y deflection signals, the X deflection signal outputs of said generators being connected in series with each other and to the X deflection coils of each of said cathode ray tubes, the Y deflection signal outputs of each of said signal generators being connected in series with each other and to the Y deflection coils of each of said cathode ray tubes.
 6. The apparatus of claim 5 wherein said X deflection coils are connected in series with each other and said Y deflection coils are connected in series with each other.
 7. The apparatus of claim 5 wherein said X deflection coils are connected in parallel with each other and said Y deflection coils are connected in parallel with each other.
 8. The apparatus of claim 5 wherein said second signal generator further provides an intensity signal which is applied to the electron beam of said auxiliary cathode ray tube such that the image produced thereby is pulsated.
 9. The apparatus of claim 5 wherein said second signal generator controls the deflection signals applied to the electron beam of said auxiliary cathode ray tube such that the image produced thereby is in the form of an easily recognizable symbol.
 10. The apparatus of claim 5 wherein said second signal generator controls the deflection and intensity signals applied to the electron beam of said auxiliary cathode ray tube such that the image produced by said auxiliary cathode ray tube is in the form of an easily recognizable pulsated symbol.
 11. The apparatus of claim 1 wherein said means comprises first and second signal generators, and first and second summing amplifiers, the X deflection signal outputs from each of said generators being connected through one of said summing amplifiers to each of the X deflection coils of said cathode ray tubes and the Y deflection signal outputs from each of said signal generators being connected through the other of said summing amplifiers to the Y deflection coils of each of said cathode ray tubes.
 12. The apparatus of claim 11 wherein said X deflection coils are connected in series with each other and said Y deflection coils are connected in series with each other.
 13. The apparatus of claim 11 wherein said X deflection coils are connected in parallel with each other and said Y deflection coils are connected in parallel with each other.
 14. The apparatus of claim 1 further comprising a lens aligned to transmit said modulated probing light, and a dichroic mirror which substantially reflects light of a wavelength of that produced by said probing light source and substantially transmits light with a wavelength of that of the electron beam image produced by said auxiliary cathode ray tube, said dichroic mirror and auxiliary cathode ray tube being disposed and aligned such that said auxiliary cathode ray tube electron beam image is projected through said dichroic mirror toward said viewing screen, said modulated probing light being substantially reflected toward said viewing screen on which said electron beam image and information image are simultaneously displayed.
 15. The apparatus of claim 14 wherein the storage medium of said information storage cathode ray tube is a plate of photochromic glass comprising a plurality of optical fibers made of photochromic glass arranged in parallel relationship such that the opposite ends of said optical fibers form the two surfaces of said photochromic glass plate, and said means comprises first and second signal generators, and first and second summing amplifiers, the X deflection signal outputs from each of said generators being connected through one of said summing amplifiers to each of the X deflection coils of said cathode ray tubes and the Y deflection signal outputs from each of said signal generators being connected through the other of said summing amplifiers to the Y deflection coils of each of said cathode ray tubes.
 16. The apparatus of claim 1 wherein said beam splitter is dichroic in that it partially reflects and partially transmits light with a wavelength of that produced by said probing light source and substantially wholly transmits light with a wavelength of that of the electron beam image produced by said auxiliary cathode ray tube, said auxiliary cathode ray tube being disposed such that said electron beam image is projected through said beam splitter and aligned with said information image.
 17. The apparatus of claim 16 wherein the storage medium of said information storage cathode ray tube is a plate of photochromic glass comprising a plurality of optical fibers made of photochromic glass arranged in parallel relationship such that the opposite ends of said optical fibers form the two surfaces of said photochromic glass plate, and said means comprises first and second signal generators, and first and second summing amplifiers, the X deflection signal outputs from each of said generators being connected through one of said summing amplifiers to each of the X deflection coils of said cathoDe ray tubes and the Y deflection signal outputs from each of said signal generators being connected through the other of said summing amplifiers to the Y deflection coils of each of said cathode ray tubes.
 18. The apparatus of claim 1 wherein the storage medium of said information storage cathode ray tube is a plate of photochromic glass. 